Abstract

Raspberry beetle (Byturus tomentosus) is a major pest of cultivated raspberries (Rubus idaeus) in Europe. In the absence of plant resistance or natural enemies, the control depends on the application of insecticides close to flowering or harvest. A better understanding of the processes used by raspberry beetles for host recognition suggests that an alternative to insecticidal control is feasible. Adults use visual and olfactory cues to locate raspberry flowers in which they feed and mate. White sticky traps, which mimic floral spectral reflectance patterns, were shown to be effective for monitoring raspberry beetle flight activity. To avoid unnecessary insecticide use, control thresholds have been developed, based on relationships between numbers of trapped adult raspberry beetles and subsequent larval damage to fruit. Trap efficacy was highest when the beetles were active in warm weather before raspberries started to flower, and declined after flowering had started. Two components of the many volatile compounds emitted by raspberry flowers were selected in electrophysiological and behavioural studies. The addition of either of these volatile compounds to white sticky traps increased the numbers of raspberry beetles caught by the traps, and one of them increased the daily catch of raspberry beetles by 2-20 times in field tests, compared with the standard traps. In preliminary experiments to determine the effective trapping area, the volatile-enhanced traps caught marked beetles 5 m from release sites. The potential use of volatile-enhanced white traps to "lure and kill" adult raspberry beetles is proposed as an alternative to insecticide control.